Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process which etches one material faster than another helping e.g. a pattern transfer process proceed. Such an etch process is said to be selective to the more rapidly etched material. As a result of the diversity of materials, circuits and processes, etch processes have been developed having selectivity towards a variety of materials.
Siconi™ is used to refer to a class of remote plasma assisted dry etch processes which involve the simultaneous exposure of a substrate to hydrogen- and fluorine-containing plasma effluents. Remote plasma excitation of the hydrogen and fluorine species allows substrate processing with low plasma-damage. Siconi™ etches have been developed which are largely conformal and selective towards silicon oxide layers while not readily etching silicon regardless of whether the silicon is amorphous, crystalline or polycrystalline. The selectivity provides advantages for applications such as tuning a gapfill profile, removing oxide pads and recessing oxide gapfill. Siconi™ etch processes also remove other silicon-containing dielectric layers such as silicon nitride and silicon oxynitride.
Siconi™ process, to date, produce solid by-products which grow on the surface of the substrate as substrate material is removed. These self-limiting processes etch more slowly as the solid by-products accumulate and the progress would eventually stop. The solid by-products are subsequently removed via sublimation when the temperature of the substrate is raised. Etch-sublimation cycles may be repeated to remove larger thicknesses of a silicon-containing dielectric layer.
Additional Methods are desirable which increase the effective etch rate of dielectric layers for some applications.